1. Field of the Invention
The present invention relates to method of and apparatus for determining the amount of impurity mixed in gas.
2. Description of Related Art
In a conventional method of determining the amount of impurity in gas with the use of an infrared spectrometer, when measuring the concentration of a trace impurity gas, the infrared absorption peak of the main component gas overlaps the infrared absorption peak of the trace gas component, causing the measurement of the trace impurity gas to be very difficult.
The following description will discuss, by way of example, a measurement of a trace moisture contained, as impurity gas, in ammonia gas.
There has conventionally been proposed a method of measuring such a trace moisture at a wavenumber at which the infrared absorption of ammonia and the infrared absorption of the moisture do not overlap each other (Japanese Patent Laid-Open Publication No. 2001-228085).
However, even by this method of measurement at a wavenumber at which the infrared absorption of ammonia and the infrared absorption of the moisture do not overlap each other, when the concentration of impurity gas is very small, the infrared absorption spectrum of the impurity gas overlaps the infrared absorption spectrum of ammonia. This makes the measurement of the concentration of the impurity gas makes difficult.
In view of the foregoing, it is an object of the present invention to provide method of and apparatus for determining the amount of impurity in gas, capable of accurately measuring the concentration of the impurity gas even though the impurity gas concentration is very small.